Adjustable cam member



Oct. 13, 1959 2 Sheets-Sheet 1 Filed April 10, 1957 R Wm My 3 W w M [V P a a m 2 .A" a V M J J. PIGNONE ADJUSTABLE CAM MEMBER 2 Sheets-Sheet 2 JOSEPH PIG/VONE INVEN TOR.

V Oct. 13, 1959 Filed April 10, 1957 United States Patent ADJUSTABLE CAM MEMBER Joseph Pignone, West Orange, N.J., assignor, by mesne assignments, to Daystrom, Incorporated, Murray Hill, N.J., a corporation of New Jersey Application'April 10, 1957, Serial No. 651,992

13' Claims. (Cl. 200-153) This invention relates to a system of adjustable point switching" to control altitude, function or process, or to throttle or modulate predetermined portions thereof, and more particularly to an adjustable cam switch for use with suchautomatic controlling and/or other apparatus.

Recorders of the type with which this invention may be-used are useful in providing a measurement and record of variable conditions such as, for example, temperature. However, they are also designed to measure and record output from such primary elements as thermocouples, tachometer generators, photoelectric cells, resistance thermometer bulbs, and any transducer that provides an electrical output which varies in accordance'with changes in a condition to be measured. Such recorders can also be employed to measure flow, pressure and weight by using suitable converters to provide an electrical output.

The indication and recording of the instantaneous state ofavariable condition by a self-balancing potentiometric recorder is accomplished by electrical networks which are adapted to be unbalanced by a variation in the condition and to elfect an operation of a suitable rebalancing means, including a potentiometer slide wire circuit with a movable. brush contact. Such rebalancing operations may include the actuation of suitable power means for simultaneously moving aninking pen or stylus over a power-driven, constantly-movable, calibrated chart.

One or more control switches, which may bemade in accordance with the invention described and claimed in my'co-pending application, Serial No. 639,822, filed February 12', 1 957, and entitled Control Switch and Circuit, are adapted for attachment to a potentiometric the continuous track with one or the other of the porv tions of the segmented track.

-In accordance with the present application, I propose to use a single or multiple'adjustable cam and switch unit which, with the aid of simple hand tools, can be secured to actuating mechanism for movement with the brush contact of the potentiometer circuit. In accordance with the present. invention, I provide not only an elfective means. of setting positionallyand clamping a cam member, associated with a switch, to its 'shaft, but I also provide a. structure in which additional cam and switch elements may be installed with minimum effort.

Generally, the invention of the present case may be embodied as an alarm switch which may also have a control function. It includes a desirably molded disc provided with an approximately 675 cam surface, en-,

r 2,908,790 I Patented Oct. 13, 1959 surface. The cam disc is provided, respectively, with holes and recesses to receive two preferably identicallyshaped lock levers, and a clamp shoe. One lock lever is located to project beyond the periphery of the cam disc for finger actuation, while the other is disposed inside of the disc periphery and intended to be moved by a rod or tool to adjust initially for manufacturing tolerances and later to compensate for wear between the other lock lever and the clamp shoe.

The cam members are carried on a circumferentially grooved mandrel slotted parallel to its axis to receive a cam stop-rod which, in turn, is clamped in place by a retaining ring having separated ends providing a throat. The throat of the retaining ring may be angularly positioned to clear said stop-rod to permit removal thereof. The parallel slot in the mandrel also serves to allow passage of a stop-tab on the clamp shoe in assembling a cam member and its clamp shoe.

An object of this invention is to provide an adjustable cam switch having effective means for positioually setting a cam member or disc and clamping it to its shaft.

An object of this invention is to provide a structure on which cam discs and switch elements may be installed Withminimum effort.

An object of this invention is to provide a cam switch including a molded, positionally-adjustable 'disc formed the-pivot stud, and a clamp shoe for adjustably positioning said disc on a carrying mandrel, the hub portion of the lock lever being cam shaped and engageable with said clamp shoe for moving it to and from clamping; position.

An object of this invention is to provide an arrangement as described in the preceding paragraph, but inwhich there are two of said lock levers, each with a pivot stud projecting from the hub portion thereof, and the cam disc has a recess to receive said two levers and aper tures for the reception of their pivot studs, and the hub portions. of both of said lock levers are cam shaped and each engageable with one of the terminals of the clamping shoe so that, upon tuming each lock lever about itspivot stud, the clamping shoe may be contracted and expand'ed to and from the mandrel-gripping position.

An object of this invention is to provide an arrange.- ment, as described in the preceding paragraph, in which one of the lock levers is located to project beyond the periphery of the cam disc for finger operation, and the other lock lever is entirely within the periphery of the cam disc so as to be movable only by a tool to adjust initially for manufacturing tolerances and later to com pensate for wear between the first-mentioned lock leverand the clamp. shoe.

These and other objects. and advantages will become apparent from the. following detailed description when taken with the. accompanying drawings. It will be underand do not define the scope or limits of the invention,-

reference being had for the latter purpose to the appended claims. 7

In the drawings, wherein like, reference characters denote like parts in the. several views-z Figure 1 is a diagrammatic view of a potentiometer and control circuit, including members embodying my invention, which may be used for controlling the temperature of a furnace and/or providing an alarm signal;

Figure 2 is an elevational view of one of the cam disc assemblies with its protective plate removed to expose its pocket and the locking parts therein;

, Figure 3 is an isometric view, with parts in vertical section, of an end portion of the cam disc mandrel;

Figure 4 is a fragmentary transverse sectional view of a modified form of one of the adjusting lock lever pivot studs;

Figure 5 is a fragmentary vertical sectional view on the line V-V of Figure 7, in the direction of the arrows;

Figure 6 is an elevational View of one of the cam disc assemblies illustrated in Figure 2, combined with its mandrel and associated parts;

Figure 7 is a detailed elevational view of one embodiment of my adjustable cam switch assembly, which may be, as an example only, mounted on the rear of the door of automatic indicating, recording and controlling apparatus, also showing the opposite face of the cam disc of Figure 2.

Referring first to Figure 1, there is shown a cam switch assembly 121 embodying my invention, for regulating a condition, shutting off media determining the condition, or giving an indication or alarm as to the condition; in this case the temperature in a furnace 13. The furnace is shown as supplied with heat from an electrical resistor or heating element 14 which receives electrical energy from a suitable source of power. Here, the power is directed through a lead 16 and a return lead 19, controlled by a contactor relay 21.

The condition or temperature of the furnace 13 is measured by a device sensitive to the condition, such as a thermocouple 23. Such thermocouple is inserted through an opening in the furnace wall and connected to an automatically balancing potentiometer circuit 161 through leads 24 and 25. As shown diagrammatically, the balancing or measuring circuit comprises a circular resistance wire 26 connected across a source of fixed voltage, such as the battery 27, through an adjustable resistor 28 and fixed resistors 29 and 31. The lead 24 is connected to this circuit through fixed resistors 32 and 33. The voltage of the thermocouple 23 is opposed by the potential drop across the measuring circuit as determined by the position of a rotatable contact member or slider 34 engaging the resistor 26.

Connected between the thermocouple 23 and the potentiometer slider 34 is a vibrator or chopper 35 and the primary winding of a transformer 36. The vibrator 35 is adapted to open and close the thermocouple circuit at a frequency of 60 cycles per second and thereby apply to the transformer primary winding a pulsating voltage having a magnitude depending upon the difference between the voltage generated by the thermocouple and the opposing output voltage of the measuring circuit. Specifically, the pulsating current flowing in the primary winding of the transformer 36 is in a direction and of a magnitude depending upon the extent of circuit unbalance and constitutes what is generally termed an error signal. The secondary winding for transformer 36 is connected directly to the input of an electronic amplifier 37 which is energized, through the leads 44, 45 from a 60 cycle power source upon closure of the switch 43.

The output of the amplifier 37 is connected to one of the field windings 38 of a two-phase motor 39 through leads 41 and 42. The other field winding 40 of the motor 39 is connected to a 60 cycle power line through leads 20 and 30 and the capacitor 22. As is well known in this art, the system normally is in a balanced condition. A change in the furnace temperature results in a corresponding change in the thermocouple voltage thereby unbalancing the system in a direction and to an extent corresponding to the deviation in the furnace temperature. Upon such system unbalance, the amplifier energizes the 4 motor for rotation in one or the other direction and the slider 34 is rotated, through the shaft or other mechanical linkage 47, to reestablish a balance of the system at a new point. Such new balance point corresponds to the new temperature of the furnace.

The motor 39, in addition to driving the potentiometer slider 34, may also serve to move a pen or stylus across a chart, as by means of a shaft and/ or other mechanical linkage, as disclosed, for example, in my co-pending application previously referred to. The motor 39 also, through the mechanical linkage or connection 57, moves the indicating pointer 58 of the instrument along a calibrated temperature scale 59. As indicated diagrammatically at 61, the motor armature may also be mechanically coupled to a tab or tabs for actuation of a tumbler cam or cams and a brush contact or contacts for a con trol switch or switches, as also disclosed in my referredto co-pending application.

The position of the slider 34 corresponds precisely to the temperature of the furnace (in terms of thermocouple voltage) as indicated by the position of the indicating pointer 58, relative to the scale 59 of temperature values, and the position of the effective operating point of a control switch, if used as in my co-pending application, for example, is indicated by a suitable pointer or index 52, which may be mechanically coupled to the control switch by suitable means 53, not fully shown in the drawings.

The adjustable cam switch assembly suitable for alarm and/or furnace control purposes may be carried by a plate 133 secured to a suitable portion of the instrument with which used and as shown most clearly in Figures 5 and 7. The means for so securing the plate 133 may be four screws 140 and associated nuts and lock washers, as illustrated. The plate 133 is apertured to receive that portion of a bearing 134 rearwardly or inwardly of a collar or flange 122 outstanding therefrom. The hearing may be of the roller type. A shaft 135 is rotatably mounted in the bearing 134 and carries a drum or pulley 136 secured thereto by suitable means, such as a set screw 137 threaded into the hub of the pulley 136 and engaging a portion 138 of reduced diameter on the shaft 135. This securing means is desirably in duplicate, that is, also including a set screw 139 extending into the hub portion of the pulley 136 at an angle of with respect to the set screw 137. v

The pulley 136 is for driving the shaft simultaneously with and at the same speed as the potentiometer slider 34 illustrated in Figure 1. In other Words, as the slider 34 is turned by the motor 39, the drum or pulley 141 carried thereon drives the shaft 135 by means of a cable, belt or chain 142 which encircles it as well as the pulley 136 on the shaft 135 (see Figures 1 and 5). In view of the fact that the pulleys 136 and 141 are of the same size, the shaft 135 is turned with and at the same speed as the shaft 47 and its slider 34.

The shaft 135 carries a mandrel or hollow shaft 143 which, as shown most clearly in Figure 3, is formed with a longitudinal or axial aperture 144 closely receiving the end portion of the shaft 135 remote from the pulley 136. As shown in Figure 7, the mandrel is secured to the shaft by means of a pair of set screws 145 threaded into the mandrel 143, desirably extending at right angles to one another. The mandrel 143 also has an enlargement 147 of its aperture 144 which loosely receives the adjacent end portion of the bearing 134, see Figure 5.

The plate-adjacent end of the mandrel 143 is formed with a flange 148 desirably spaced from the plate 133 by a washer 149. Said flange carries a limit-rod 151 projecting radially therefrom and engageable with a setscrew 152, threaded into the plate 133, for the purpose of limiting turning of the mandrel 143. As shown in Figure 5, the mandrel 143 is formed with a series of equallyspaced relatively deep circumferential grooves 150 alternating with a series of narrower and shallower grooves 153,. and a straight groove 154 extending along its periphery parallel to. its axis, and intersecting thecircumferential grooves 150 and 153, for a purpose which will be'later explained more fully. The groove 154 is desirably slightly wider than the grooves 150 but of the same-radial depth. These grooves serve for the desired mounting of one or more switch cams or cam members or. discs155,

Reference is now made to Figure 7. Each disc 155 is desirably formed of molded insulating material. It is provided. with a groovedefined by inner and outer generally cylindrical surfaces, the former of which makes a cam surface 156 extending therearound for about 700 and comprising a low, inner, or relatively-small radius rim. or dwell. 157 coaxial with and joining a high, outer, or relatively-large radius rim or dwell 158 along an inclined portion or ram 159. Each disc 155 is adjustably mounted onthe mandrel 143 so that it may operate an associated switch 60- (one of which is provided for each cam disc) between either end of a travel of the brush contact 34- along the potentiometer wire 26 of nearly 350*, or more exactly about 337.5 Each switch 60 is desirably a single-pole double-throw switch having a follower pin 162 engaging the cam surface 156 and actuable one way or the other as said pin rides up or down on the inclined connecting portion 159 of said cam surface. Each cam member 155 carries one or a pair of cam locking means or lock levers, 163 and 164, which lever or each of which levers has a pivot stud, 165 and 166, projecting from a hub portion thereof. Reference also: is now made to Figure 2, which shows the reverse side-of the cam member 155. The cam member is recessed, asindicated at 167 to receive the lock levers, 163 and 164, which recess includes a circular portion to receive a shaft clamping member or shoe 168. The discis appropriately apertured to receive the lock lever pivot studs 165 and 166, preferably tightly enough; so that the lock levers stay in position until moved. The lock levers of each disc serve for the actuation of a clutch device, such as the clamp shoe 168, carrying an axially offset key-cam stop member 160. The member 160" may be spot welded to a side of the clutch device 168 and has an inner radially-projecting lug 169 receivable in a selected circumferential groove 150 formed in the mandrel.143,, see also Figure 3. The clamp shoe 168 includesa pair of spaced fingers 171 and 172, projecting in. generally radial directions. The clamp shoe has an edge portion cut oi, as indicated at 170, to improve its gripping action, and when free, fits the mandrel closely but. without gripping it.

It will be noted that circular end portion, or hub portion, of the lock levers 163' and 164 is eccentric with.

respect to the associated studs 165 and 166. Consequently, rotation: of the lever will cause the peripheral surface to approach, or recede' from, the adjacent fingers 171 and 17260)? the clamping member 168.

The lock lever 163, the hub portion of which engages the longer finger 171, is located to project beyond the normal or circular periphery of the cam disc, or to a radius beyond the normal or circular outline thereof, for finger actuation. The other lock lever 164 is for adjusting purposes and. desirably is disposed entirely within the circular. outline or periphery of the disc so as to be movable only by a tool to adjust the tightness of the clamp shoe 168' about the mandrel initially for manufacturing tolerances; and later to compensate for wear between the lock lever 163 and said clamp shoe. The pivot stud166 ofthis lock lever 164, in the alternative form of Figure 4, has special means for 'snubbing its movement,.such as a transverse aperture 173 therethrough and a. compression spring 174 carried therein and with its; ends. engaging its cam disc 155 to create a drag.

Both. of the: lock levers 163 and 164 are movable toward and away from the lobe or portion 175 of the disc projecting beyond' the circular periphery thereof.

The

lever hubs being of theillustrated cam shape. and engaging the respective fingers, movement thereof away and to clearly show the switch-operating position, there" is also provided an indicator extension or lug 176, desirably painted White or other contrasting color, which coincides in position with the midpoint of the inclined portion 159 of the cam surface 156 (see Figure 7), and three other extensions or lugs 177, 178 and 179, which facilitate rotary movement of the cam member during adjustment thereof on the mandrel.

After assembly with each cam member 155, the lock levers 163 and 164 and their associated clamp shoe 168 are desirably enclosed in. the recess 167 by means of a metal cover plate 181, see Figure 5,.whereby the parts are. prevented from misplacement. In order to insure that the clamp shoe of a given cam disc stays in the proper groove 150, afterreaching it by moving the stop tab 169 of said clamp shoe along the groove 154' to the groove 150 which. has been selected, and that it is limited. in turning movement about the mandrel, I provide a stop rod 182-Which is received in the groove 154 and, after such reception, held in place by means of an outerretaining ring 183 clamping in one of the shallower grooves 153.. This retaining ring is open at one place to form a throat 184 (see. Figure 7) so that upon rotation, itsthroat may be positioned to clear the stop rod 182 for rod'release;

It is: desirable to provide two lock levers 163 and 164 for each cam disc. Initially, the lever 164 is rotated somewhat ina clockwise direction to a point such that rotation of thel'ever 163' in a counter-clockwise direction will deflect the finger 171 sufficiently to cause the clamp shoe 1 .68 to grip tightly about. the supporting mandrel. In the event that the cam action of the lock lever 163- does, after moving all the way from the lobe 1-75', allow the shoe to loosen, the tension provided for by said lever can be adjusted as follows. first moved clockwise to the fully unlocked position illustrated in Figure 6 The adjusting lever 164 is then .moved clockwise slightly from its position there illustrated, as by inserting a paper clip or some similar tool into the forked groove provided in its end. Then, the" locking lever 163 is moved counter-clockwise, as from the position of Figure 6 to the dotted-line position illustrated in Figure 2-or beyond, to push the terminal 171 toward the terminal 172 and thereby lock the switch cam on the mandrel 1 43. The locking lever 163 should look when it is approximately midway between the lobes or extensions and 178. If it does not, the lever 164 should be readjusted. After this, an attempt should be made to turn the switch cam 155 to find out if it is tight on the mandrel.

After the mandrel, shaft and bearing are assembled, as viewed in Figure 5, the first assembled cam disc 155 is inserted over the mandrel, after removing the outer retaining ring 183- and the stop rod 182. First, however, the washer 185 is applied, which besides spacing the cover plate from the flange 148, serves to hold .the flangeadjacent end of the stop rod 182 in the groove 154. Each cam disc is provided with a cover plate 181, to retain the parts of the cam member in operative position, corresponding apertures therein receiving the lugs outstanding from the face of thecam member 155 viewed in Figure 2; The absence of the stop. rod 182 allows the stop tab 169to travel with the assembled parts along the straight groove 154 until the assembly abuts against the washer as shown in Figure 5.

is followed by turning. the cam disc 155 and its associated parts to the desired angular position on the mandrel and then clamping it tightly in place thereon by The lock lever 163 is simply moving the lever 164 and/or the lever 163 away from the lobe 175. A spring wire retainer 186, shaped generally like the retaining ring 183 but formed of lighter material for more convenient operation, is receivable in one of the shallower grooves 153, to prevent axial movement of the cam member along the mandrel.

If it is desired to use more than one switch cam, the others are applied in identical manner, up to a selected number in accordance with the capacity of the mandrel 143 illustrated in Figure 3. The last or exterior switch cam may be securely held in place, after reapplication of the stop rod 182, by reapplying the retaining ring 183, which, for the last cam, may take the place of a wire retainer 186 referred to. It will, however, be understood that all of the retaining members (that is, that designated 1 86 and the intermediate ones similarly positioned) may correspond in size and structure with the outer retaining ring 183, illustrated in Figure 2, although it is preferred that they may be made from light spring wire for the reason mentioned and to avoid the necessity of using a tool.

As shown in Figure 7, each cam disc 155 has associated therewith a snap-action switch 60 which is actuated to the closed or open position by movement of the lever 189 which carries a follower pin 162. When the follower pin 162 rides along the inner rim or low dwell 157 of the cam disc, the switch contacts will be, say, closed, whereas when the pin rides along the outer rim or high dwell 158, the switch contacts are open. Movement of the switch contacts to the open or closed position occurs when the follower pin is approximately midway on the connecting track 159 which joins the low and high dwell portions 157 and 158. Since the entire cam plate, or disc 155, can be set to any desired angular position on the mandrel, it will be apparent that the switch contacts can be made to open or close at any point within the range of the recorder, it being pointed out that the mandrel 143 rotates simultaneously with the slider through the pulley 136 and cable 142, see Figure 5.

Referring now to Figure 1, when the follower pin 162 rides along the inner dwell 156 of the assembled cam (here designated 121) the indication of the instrument pointer 58 will be to the left (or low side) of the alarm set-point as indicated by the index 52. In such case, the contacts of the switch 60 will be closed, thereby completing the circuit between the battery 202, indicator lamp 201 and the energizing coil of the relay 21, whereupon the furnace heater is connected to its source of power. As the furnace temperature increases and approaches the set point the sloping, or inclined surface 159 drives the pin 162 downward and, as .the set point is reached, the contacts of the switch 60 will be opened thereby deenergizing the furnace heater. It is apparent, therefore, that each combination of a cam member and switch may serve to energize appropriate signal means to designate the condition of the furnace and/or to actually control the furnace temperature. As shown in Figure 5, a plurality of such cam members are mounted in series on the single mandrel 143, each member being associated there with a switch 60, such switches being secured in operative position on the mounting plate 133 as by nuts and bolts 197, 198 and/or screws 199.

The setting of each individual switch cam, as for alarm purposes, is easily accomplished and will now be described. All of the alarm switches may be set in the same manner. The pointer 52 is manually moved so that it indicates the reading at which the switch is to operate and the cover 194, see Figure 5, is removed. A selected cam is loosened with respect to the mandrel or shaft 143 on which it is mounted, by manually moving the cam lock lever 163 toward the stop afiorded by projected lobe 175, see Figure 6. The switch cam assembly is then manually rotated until the raised or high dwell portion of the cam track actuates the switch lever, which makes or breaks contact through switch 60. In the case of a snap-action switch, the movement of the contacts audible click.

If circumstances are such that the click cannot be heard, a test light or an ohmmeter may be connected across the terminals of the switch to check the point of contact. The switch cam is then rotated slowly back and forth several times, stopping at the point where the switch makes contact. When this is accomplished, the cam lock lever 163 is moved away from the projecting lobe .175 to thereby tighten the clamp shoe 168 and lock the switch cam on the mandrel or shaft 143. To doublecheck this set point, the pointer 58 may be moved back and forth until a click is heard. The pointer 58 will then register on the set point shown by the pointer 52 at the instant the switch clicks.

From the foregoing disclosure, it will be seen that I have provided an adjustable switch cam assembly involving one or more cam discs and associated switches usable with or without automatic controlling apparatus in order to provide for the establishment of one or more alarm circuits at a predetermined position or positions. The adjustment of any or all cam members is accomplished simply and quickly without the need of tools and Without requiring removal of the members from the supporting mandrel. Inasmuch as each cam member is secured to, and loosened from, the mandrel by mo'vemnet of the single lock lever having a readily accessible end, the cam members need be spaced apart only a small distance on the mandrel. The locking pin 182, which is disposed in the longitudinal slot formed in the mandrel, see Figure 5, serves as a positive stop limiting the angular extent to which all of the cam members may be rotated on the mandrel. Consequently, it is impossible for the user to rotate a cam member more than one revolution to thereby set the cam member improperly with respect to the potentiometer slider. Removal of such locking pin clears the longitudinal channel in the mandrel for passage therealong of the radial tab 169, see Figure 2, for removal of the cam niember from the mandrel. The provision of the normally-fixed lock lever, to take up for wear in the clamping shoe, provides a convenient means for obtaining the required clamping force to securely hold the cam member in the set position.

Having now described my invention in detail in accordance with requirements of the patent statutes, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims. a

I claim: 3

1. A circular cam member comprising a body element having an outer peripheral surface forming one dwell, a groove defined by inner and outer generally cylindrical surfaces and formed in one face coaxial with said outer surface and making another dwell, and an inclined surface extending from the inner generally cylindrical surface at one end of said groove and forming a ramp between it and said outer peripheral surface.

2. The invention as recited in claim 1, in which there is a projection on said outer peripheral surface positioned radially of said inclined portion.

3. A cam member adapted for mounting on a generally cylindrical shaft and adjustable thereon to any desired angular position comprising a pocketed body member provided with a hole for receivingsaid shaft, a shaftclamping member disposed in said pocket in the body member, and manually-operable means engageable with said shaft-clamping member to adjust its tension for clamping it in adjusted position on and in direct engagement with said shaft or releasing it with respect thereto.

4. A cam member adapted for mounting on a shaft and adjustable thereon to a predetermined angular position comprising a pocketed body member provided with a hole for receiving said shaft, a shaft clamping member disposed in said pocket in the body member and including projecting arms, a stop abutting one of said arms, and a manually-operable lever pivoted with respect to the body member and having an eccentric hub portion engageable with the other of said arms to cause the shaft-clamping member to contract about an associated shaft for clamping it in adjusted positionon said shaft or releasing it with respect thereto.

5. The invention as recited in claim 4, wherein the said stop is a lever pivoted with respect to the body member and having an eccentric hub portion abutting the said one arm.

6. The invention as recited in claim 4, in which said lever has a stud pivoting it to the body member, said stud having a transverse aperture, and a spring mounted in said aperture and engaging said body member to snub rotative movement thereof.

7. The invention as recited in claim 4, in which the shaft-clamping member has a radial, inwardly-extending tab slidable in a groove provided in the shaft.

8. An adjustable cam switch assembly, comprising a cam member mounted for rotative movement and formed with a cam surface comprising low and high dwells joined by an inclined portion, a lock lever with a pivot stud projecting from a hub portion thereof, said cam member having a recess and an aperture for the respective reception of the lock lever and the pivot stud, and a clamping member for adjustably clamping said cam member on a carrying mandrel, the hub portion of said lock lever being cam-shaped and engageable with said clamping member for moving it to and from the mandrel-clamping position.

9. The invention as recited in claim 8, in combination with a carrying mandrel having a series of axially spaced circumferential grooves and a peripheral groove extending parallel to its axis, and the clamping member has a radially projecting stop-tab receivable in a selected circumferential groove and a pair of spaced arms, the hub portion of said lock lever being engageable with one of said arms for moving the clamping member to and from mandrel-gripping position upon pivotal movement of the lock lever.

10. The invention as recited in claim 9, in which there are two of said lock levers, each with a pivot stud projecting from a hub portion thereof, and said cam member has a recess to receive said two levers and apertures for the reception of their pivot studs, and in which the hub portions of both of said lock levers are cam-shaped and each engageable with one of the arms of the clamping member for moving the clamping member toward and from mandrel-gripping position, one of said levers being located to project beyond the periphery of the cam member for finger operation and the other lever being entirely within the periphery of the cam member.

11. The invention as recited in claim 10, in which one of said pivot studs has a transverse aperture and there is a compression coil spring carried in said aperture with its ends engaging the cam member to create a drag against movement of the lever.

12. In combination, an adjustable cam switch assembly comprising a cam disc carrying mandrel, said mandrel having a circumferential groove and a peripheral groove extending parallel to its axis, a cam disc mounted on said mandrel, said cam disc being formed with a cam surface comprising a low dwell coaxial with and joining a high dwell along an inclined portion, a switch associated with the cam disc, said switch having a follower pin engaging the cam surface, a lock lever with a Pivot stud projecting from a hub portion thereof, said cam disc having a recess to receive the lock lever and an aperture for the reception of the pivot stud, and a clamp shoe with a projecting offset stop-tab receivable in said circumferential mandrel groove and a pair of spaced terminals, the hub portion of said lock lever being camshaped and engageable with one of said terminals for, upon turning about its pivot stud, moving the clamp shoe to and from mandrel-gripping position.

. 13. In combination, a carrying plate, an adjustable cam switch assembly comprising a bearing carried by said plate, a shaft rotatably mounted in said bearing, a pulley carried by said shaft and causing it to turn, a cam disc carrying mandrel on said shaft, said mandrel having an outstanding flange at the end adjacent said plate, a stop rod projecting radially from said flange, a stop screw threaded into said plate for engagement by said rod to limit mandrel turning, means holding said mandrel on said shaft for turning comprising a portion of reduced section on said shaft and a pair of set screws extending at an angle to one another from said mandrel and engaging said portion of reduced section, said mandrel having a [series of axially spaced circumferential grooves and a peripheral groove extending parallel to its axis, a plurality of molded cam discs mounted on said mandrel, a resilient spacer receivable in a circumferential groove between adjacent cams, each cam disc being.

formed with a cam surface extending therearound and comprising a low dwell coaxial with and joining a high dwell along an inclined portion, making the cam switch assembly adjustable to operate between either end of the slider travel along the potentiometer wire, a singlepole double-throw switch associated with each cam disc, each switch having a follower pin engaging its cam surface, two lock levers, each With a pivot stud projecting from a hub portion thereof, each cam disc having a recess to receive the two lock levers and apertures for the reception of their pivot studs, a clamp shoe with a projecting offset stop-tab receivable in one of said circumferential mandrel grooves and a .pair of spaced terminals, the hub portions of said lock levers being cam-shaped and each engageable with one of said terminals for, upon turning the lever about its pivot stud, moving the clamp shoe to and from mandrel-gripping position, one of said lock levers being located to project beyond the periphery of the cam disc for finger actuation, the other lock lever being entirely within the periphery of the cam disc so as to be movable only by a tool to adjust initially for manufacturing tolerances and later to compensate for wear between the first-mentioned lock lever and the clamp shoe, a cover plate to overlie the lock levers and clamp shoe for each cam disc and confine them in the recess, a cam disc stop-rod receivable in said parallel groove in the mandrel, and a retaining ring for clamping said stop-rod in place, said ring being open at one place to form a throat so that, upon rotation if necessary, its throat may be positioned to clear the stop-rod for its release, said parallel groove also serving to permit the stop-tab to pass along the mandrel in assembling and disassembling the cam disc and clamp shoe units with respect to said mandrel.

References Cited in the file of this patent UNITED STATES PATENTS 2,044,607 Garrett June 16, 1936 2,499,679 Pianta Mar. 7, 1950 2,546,077 Peter Mar. 20, 1951 2,779,827 Brown et al. Jan. 29, 1957 

